An oil pump to pressurize and discharge oil (e.g., a working fluid) by power supplied from a driving source, such as an engine, so as to supply hydraulic pressure to a hydraulic controller is widely used in power transmission apparatuses, such as automatic transmissions. Such an oil pump may include a plurality of suction ports through which oil is sucked, and may pressurize and discharge oil merged inside the oil pump.
For example, Patent Document 1 discloses an oil pump disposed between a strainer located in a lower portion of a transmission case and a hydraulic controller attached to a lateral portion of the transmission case. Oil sucked from a reservoir through the strainer and oil as an excess pressure discharged from the hydraulic controller merge inside a housing of the oil pump. The housing of the oil pump is provided with: a gear housing chamber housing an external gear and an internal gear; a suction oil passage through which oil in the reservoir is sucked from a first side of the radial direction of the external gear through the strainer; a reflux oil passage through which oil as an excess pressure discharged inside the hydraulic controller is refluxed from a second side of the radial direction; and a junction where the suction oil passage and the reflux oil passage join. Thus, when viewed in the axial direction of the rotation shaft, oil flowing from the reservoir through the suction oil passage and oil flowing from the hydraulic controller through the reflux oil passage face each other at the junction.